1. Field of the Invention
The present invention relates to a platelet-type zirconium phosphate and a method for preparing the same.
2. Discussion of Related Art
In general, a metal sheet (for example, a steel plate and an aluminum plate) is a material which is very important in modern industries and has been widely used for home electronic appliances, automobiles, and building materials. However, these metals have a problem in that they corrode easily since they produce a corrosion product in the air or by contact with moisture. Also, the metals show insufficient coatability with a paint, and their surfaces are easily contaminated by a user's fingerprint, etc.
To solve the above-described problems, especially to improve the corrosion resistance and fingerprint resistance, chromate treatment has been carried out.
The chromate treatment can exhibit an anti-corrosion effect in a short period of time even when chromate is used alone and also highly improve the anti-corrosion capability of a paint as a steel sheet is coated with a resin paint. Also, the chromate treatment can enhance close adhesion between the paint and the steel sheet and thus has been used as an essential process for preparing a painted steel sheet. As the use of materials, such as hexavalent chromium, lead, and mercury, which are toxic to a human body, has been inhibited all over the world, however, the chromate treatment used to improve the corrosion resistance in all steel sheets except for some steel products has been restricted.
Therefore, to replace the chromate treatment, the steel and paint manufacturers have made an effort to improve the corrosion resistance by coating a surface of a metal sheet with a resin composition for surface treatment. The resin composition is composed of a binder resin and a solvent and serves to improve the corrosion resistance of a metal sheet since a metal such as silica, phosphate, zirconium, or titanium is added as a corrosion-resistant additive. However, the additives are composed of inorganic particles and thus have problems in that the corrosion resistance in the interface may be lowered and a reduction in gloss may be caused by surface irregular reflection.
To solve the above problems, a platelet-type zirconium phosphate (ZrP) may be used as a corrosion-resistant additive to improve the corrosion resistance of a steel sheet, etc. In this case, the zirconium phosphate additive may be prepared using a method as shown in FIG. 1. That is, the zirconium phosphate additive may be prepared by mixing zirconium ions, phosphate ions, and hydrogen fluoride with water, heating the resulting mixture at 50 to 60° C. for approximately 24 hours, adding an organic modifier, and dispersing the mixture.
However, the additive prepared by the method does not have a significant effect of improving the corrosion resistance since a P—OH group is destroyed by the organic modifier, and is applicable to a water-soluble resin since it is easily dispersed in water.